«RESEARCH Open Access Biomedical engineering meets acupuncture development of a miniaturized 48-channel skin impedance measurement system for needle ...»

Litscher and Wang BioMedical Engineering OnLine 2010, 9:78

http://www.biomedical-engineering-online.com/content/9/1/78

RESEARCH Open Access

Biomedical engineering meets acupuncture development of a miniaturized 48-channel skin

impedance measurement system for needle and

laser acupuncture

Gerhard Litscher*, Lu Wang

* Correspondence: gerhard.

Abstract

litscher@medunigraz.at Research Unit of Biomedical Background: Due to controversially discussed results in scientific literature Engineering in Anesthesia and concerning changes of electrical skin impedance before and during acupuncture a Intensive Care Medicine and TCM new measurement system has been developed.

Research Center Graz, Medical University of Graz, Methods: The prototype measures and analyzes the electrical skin impedance Auenbruggerplatz 29, 8036 Graz, computer-based and simultaneously in 48 channels within a 2.5×3.5 cm matrix.

Austria Preliminary measurements in one person were performed using metal needle and violet laser (405 nm) acupuncture at the acupoint Kongzui (LU6). The new system is an improvement on devices previously developed by other researchers for this purpose.

Results: Skin impedance in the immediate surroundings of the acupoint was lowered reproducibly following needle stimulation and also violet laser stimulation.

Conclusions: A new instrumentation for skin impedance measurements is presented.

The following hypotheses suggested by our results will have to be tested in further studies: Needle acupuncture causes significant, specific local changes of electrical skin impedance parameters. Optical stimulation (violet laser) at an acupoint causes direct electrical biosignal changes.

Background The autonomic nervous system plays a key role in basic acupuncture research [1].

There are several studies evaluating the electrical properties of acupuncture points and meridians [2]. For the first time we are able to investigate possible acupuncture-specific changes in the activity of the autonomic nervous system using a newly develop

From left to right and top to bottom: Printed circuit board assembly, measurement system with grounding electrode for the wrist including a hook-and-loop fastener, sensor unit; circuit diagram; 48 spring load mounted skin electrode contact cylinders; ECG grounding electrode compared in size to the sensor part of the measurement system.

Figure 2 Acupuncture point and practical details of the new impedance measurement system.

From left to right and top to bottom: Localization of the acupuncture point Lu 6 (Kongzui); documentation of the first measurement performed at the TCM Research Center Graz (May 7, 2010); application and manual stimulation of a metal needle via the system’s guiding rail provided for this purpose; puncture site of the needle (red arrow) compared to the indentations of the miniaturized measurement cylinders (e.g. black arrow); violet laser (405 nm) stimulation between the registration sites (distance 2.5 mm).

Results and Discussion All recordings were reliable at all 48 skin sites. The first results showed very interesting changes in skin impedance in several registration channels. For example, skin impedance in the immediate surroundings of the acupoint was lowered reproducibly following manual needle stimulation (Figure 3). In case of violet laser stimulation these phenomena could also be observed in an evidence-based manner (Figure 4).

As mentioned in the background section, there are some already existing important systems. Already in 1976, Becker et al. [3] have performed very interesting measurements with a system based on the same idea (multi-channel recordings). However, the data are not directly comparable because they used different materials, different interelectrode distances and also a different recording procedure. They first investigated the skin with a meridian scanning probe (1-channel system) and then with the 36channel system. One of the main disadvantages of this previously developed system was that investigations can only be performed in the resting period, but not during acupuncture stimulation. With our system, it is possible for the first time to continuously and simultaneously monitor a region of interest (around the acupoint) even during the insertion of a metal needle or the activation/deactivation of a laser for acupuncture.

The previously existing limitations of electrodermal impedance measurements were the measurement area (point selectors with a tip only, representing a hand-held 1channel system) and related problems (pressure, angle) and also too few registration sites (in most cases only punctual measurements, no multi-channel systems)[7,8]. In contrast to our electrode configuration (electrode diameter 0.9 mm), the electrodes of the system of Colbert et al. [8] have a diameter of 4 mm and are fixed separately at the body surface with an elastic adhesive or cloth wrist band. “Confounding factors, such as skin moisture, electrode pressure, stratum corneum thickness, electrode polarization and other factors, have led many to assert that the reportedly distinct electrical characteristics are attributable to external factors and/or artifacts and not to the acupuncture point or meridian” [2]. The newly developed system allows for the first time simultaneous and continuous, acupuncture-relevant multi-channel measurements using appropriate analysis methods. As we have only performed measurements in one subject, further measurements in a great number of healthy volunteers are absolutely necessary.

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Figure 3 Analyses of the 48 channels of the impedance system during needle insertion and needle stimulation. Top: Circular chart - needle stimulation (time in sec clockwise and resistance R in kOhm from center outwards). Bottom: Changes in electrodermal impedance during manual needle stimulation (note the lowered impedance in some, but not all channels). Six channels surrounding the acupoint were randomly chosen. In this measurement, the most marked change in impedance during insertion and stimulation of the metal needle can be found in one electrode (yellow line) next (2.5 mm) to the acupoint.

Circular chart - violet laser acupuncture, details see Figure 3. Bottom: Changes in electrodermal impedance immediately following the onset of violet laser stimulation in specific registration sites only. Three channels surrounding the acupoint were randomly chosen. In this measurement, the ‘on-effect’ of the violet laser is clearly demonstrated.

The latter result (iii) could be the first proof in acupuncture research that optical stimulation (violet laser) at an acupoint causes a direct electrical biosignal change at a distance of 3 mm. This fact alone might yield answers to important core questions in acupuncture (meridian and/or placebo research), be it for further basic or clinical acupuncture research.

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project ‘Bioengineering and clinical assessment of high-tech acupuncture - A Sino-Austrian research pilot study’ (Austrian Ministries of Health and of Science and Research and the Eurasia-Pacific Uninet) and was supported by the Science Department of the City of Graz.

The Austrian Society for Controlled Acupuncture (OGKA) has awarded the scientific work described in this paper with the OGKA Scientific Award 2010 for TCM Basic Research (award ceremony on Sep 25, 2010).

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